Since pig iron and scrap are cheap, and because there is no expensive refinement process, cast iron is a low cost material compared with steel.
由于生铁和废钢铁都便宜，又因为不需要昂贵的精炼过程，和钢相比铸铁是一种廉价材料。
2
Photo 731: Flying pig made by scrap gas storage reservoir.
图731：由废旧煤气罐做成的飞天猪？
3
Raw materials can increase the amount of scrap to reduce the amount of pig iron or no iron, pig iron effective to avoid the genetic influence on the casting.